CN104271899B - Waste heat recovery plant - Google Patents

Abstract

A waste heat recovery device including a Rankine cycle capable of suppressing a decrease in the chance of operating the Rankine cycle and enabling the Rankine cycle to operate efficiently. The waste heat recovery device (1) for recovering and utilizing the waste heat of the engine (10) has: a Rankine cycle (2), and the Rankine cycle (2) has a heater (22), an expander (23), a condenser (24) and pump (25); bypass flow path (26), the bypass flow path (26) makes the refrigerant flow around the expander (23); bypass valve (27), the bypass valve (27) bypasses The flow path (26) is opened and closed; and the control unit (4). When starting the Rankine cycle (2), the control unit (4) executes the Rankine cycle (2) in which the pump (25) is operated with the bypass valve (27) open, and then the bypass valve (27) is closed. start control. In addition, when the pressure difference between the high-pressure side and the low-pressure side of the Rankine cycle (2) after closing the bypass valve (27) does not reach the startup completion judgment value within a specified time, the control unit (4) repeatedly executes the launch control.

Description

Waste heat recovery device

technical field

The present invention relates to a waste heat recovery device including a Rankine cycle that recovers waste heat from an external heat source such as an engine and regenerates it as power.

Background technique

As such a device, for example, a waste heat utilization device described in Patent Document 1 is known. The waste heat utilization device described in Patent Document 1 includes: a Rankine cycle having a pump, a heater, an expander, and a condenser; a bypass flow path bypassing the expander; and a bypass valve , the bypass valve opens and closes the bypass flow path. When starting the Rankine cycle, firstly, the bypass valve is opened to circulate the refrigerant, and when the temperature of the gas-phase refrigerant on the inlet side of the expander reaches a predetermined temperature or higher, the bypass valve is closed, and the expander and the pump are operated. The speed increases. In addition, when the pressure difference between the inlet and outlet of the expander (expander differential pressure) reaches a predetermined differential pressure after the bypass valve is closed, it is determined that the startup of the Rankine cycle is completed.

prior art literature

patent documents

Patent Document 1: Japanese Patent Laid-Open No. 2009-97387

Contents of the invention

The technical problem to be solved by the invention

However, in the conventional waste heat utilization device described above, no consideration is given to the time until the start of the Rankine cycle is completed, that is, the time until the differential pressure of the expander reaches a predetermined differential pressure after the bypass valve is closed.

When the differential pressure of the expander reaches the specified differential pressure, if sufficient output cannot be obtained from the expander, or the differential pressure of the expander does not reach the specified differential pressure even after a certain period of time, then there is a large It is possible that the differential pressure of the expander does not reach the above-mentioned specified differential pressure for a relatively long period of time. Therefore, in the above-mentioned conventional waste heat utilization device, there is a possibility that the time during which the Rankine cycle operates (runs) in a state of poor efficiency may be prolonged.

In this regard, it is also conceivable to design that the Rankine cycle does not work when the differential pressure of the expander does not reach the specified differential pressure after a certain period of time has passed. Chances are likely to be reduced, so it's not ideal.

The present invention was made in view of the above problems, and an object of the present invention is to provide a waste heat recovery device including a Rankine cycle that suppresses a decrease in the chance of operating the Rankine cycle and enables the Rankine cycle to operate efficiently.

Technical solutions adopted to solve technical problems

A waste heat recovery device according to one aspect of the present invention includes: a Rankine cycle. The above-mentioned Rankine cycle is equipped with a heater, an expander, a condenser, and a pump in the circulation path of the refrigerant, wherein the above-mentioned heater utilizes waste heat from an external heat source to cool The refrigerant is heated to vaporize the refrigerant, the expander expands the refrigerant passing through the heater to generate power, the condenser condenses the refrigerant passing through the expander, and the pump transfers the refrigerant passing through the condenser to The above-mentioned heater sends out; the bypass flow path, the above-mentioned bypass flow path makes the refrigerant flow around the above-mentioned expander; the bypass valve, the above-mentioned bypass valve opens and closes the above-mentioned bypass flow path; the pressure difference detection part, the above-mentioned pressure a difference detection unit that detects a pressure difference between a high pressure side and a low pressure side of the Rankine cycle; and a control unit that executes start-up control of the Rankine cycle and operates the pump with the bypass valve open, Then the bypass valve is closed, and when the pressure difference after closing the bypass valve does not reach the startup completion judgment value of the Rankine cycle within a predetermined time, the control unit repeats the startup control.

A waste heat recovery device according to another aspect of the present invention includes: a Rankine cycle in which a heater, an expander, a condenser, and a pump are arranged in the circulation path of the refrigerant, wherein the heater utilizes waste heat from an external heat source to The refrigerant is heated to vaporize the refrigerant, the expander expands the refrigerant passing through the heater to generate power, the condenser condenses the refrigerant passing through the expander, and the pump transfers the refrigerant passing through the condenser sent to the above-mentioned heater; the bypass flow path, the above-mentioned bypass flow path makes the above-mentioned refrigerant flow around the above-mentioned expander; the bypass valve, the above-mentioned bypass valve opens and closes the above-mentioned bypass flow path; the pressure difference detection part, The pressure difference detection unit detects the pressure difference between the high pressure side and the low pressure side of the Rankine cycle; The above-mentioned pump works, and then closes the above-mentioned bypass valve when the above-mentioned pressure difference reaches a predetermined value. If the start completion judgment value higher than the above-mentioned first predetermined value is not reached, the above-mentioned bypass valve is opened, and then, when the above-mentioned pressure difference reaches the second predetermined value higher than the above-mentioned first predetermined value and lower than the above-mentioned start completion judgment value value, close the above-mentioned bypass valve.

Invention effect

According to the waste heat recovery device described above, when starting the Rankine cycle, after the bypass valve is closed to circulate the refrigerant through the expander from the state where the refrigerant is circulated around the expander, the high-pressure side of the Rankine cycle If the pressure difference with the low pressure side does not reach the start completion judgment value within the specified time, the bypass valve is opened to allow the refrigerant to circulate around the expander again, and then the bypass valve is closed. Thereby, it is possible to suppress the increase in the time during which the Rankine cycle is operated with poor efficiency, and to circulate the refrigerant through the expander while increasing the possibility of the Rankine cycle being activated. As a result, it is possible to efficiently operate the Rankine cycle while suppressing a decrease in the chance of operating the Rankine cycle.

Description of drawings

FIG. 1 is a diagram showing a schematic configuration of a waste heat recovery device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing Rankine start control in the embodiment.

FIG. 3 is a flowchart showing Rankine start control in the embodiment.

Fig. 4 is a timing chart of Rankine start control.

FIG. 5 is a diagram for explaining updating (incremental correction) of the valve closing determination value ΔPs1 .

6 is a diagram showing a schematic configuration of a waste heat recovery device according to a modified example of the embodiment.

FIG. 7 is a diagram for explaining another example of updating (incremental correction) of the valve closing determination value ΔPs1.

FIG. 8 is a diagram showing an example of the valve closing judgment value ΔPs1 corrected every time the Rankine cycle is started.

detailed description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a schematic configuration of a waste heat recovery device 1 according to an embodiment of the present invention. The waste heat recovery device 1 described above is mounted on a vehicle, and recovers and utilizes the waste heat of the engine 50 of the vehicle.

As shown in Figure 1, the waste heat recovery device 1 includes: a Rankine cycle 2, which recovers the waste heat of the engine 50 and converts it into power; a transmission mechanism 3, which is connected between the Rankine cycle 2 and the engine 50 and the control unit 4, the control unit 4 controls the overall operation of the waste heat recovery device 1.

The engine 50 is a water-cooled internal combustion engine, and is cooled by engine cooling water circulating in the cooling water flow path 51 . A heater 22 of a Rankine cycle 2 described later is disposed in the cooling water passage 51 so that engine cooling water absorbing heat from the engine 50 flows through the heater 22 .

The Rankine cycle 2 recovers waste heat (here, heat of engine cooling water) of the engine 50 as an external heat source, converts it into power, and outputs it.

In the refrigerant circulation passage 21 of the Rankine cycle 2, a heater 22, an expander 23, a condenser 24, and a pump 25 are arranged in this order. In addition, a bypass passage 26 is provided between the heater 22 and the condenser 24 so that the refrigerant bypasses the expander 23 to circulate, and a bypass valve 27 for opening and closing the bypass passage 26 is provided in the bypass passage 26. . In addition, the operation of the bypass valve 27 is controlled by the control unit 4 .

The heater 22 is a heat exchanger that heats the refrigerant to form superheated steam by exchanging heat between the engine cooling water that has absorbed heat from the engine 50 and the refrigerant. In addition, although not shown, the heater 22 may be configured so that the exhaust gas of the engine 50 replaces the engine cooling water, and heat exchange is performed between the exhaust gas of the engine 50 and the refrigerant.

The expander 23 is, for example, a scroll-type expander that generates power (driving force) by expanding refrigerant heated by the heater 22 to become superheated vapor and converting it into rotational energy.

The condenser 24 is a heat exchanger that cools and condenses (liquefies) the refrigerant by exchanging heat between the refrigerant that has passed through the expander 23 and the outside air.

The pump 25 is a mechanical pump that sends the refrigerant (liquid refrigerant) liquefied in the condenser 24 to the heater 22 . In addition, by sending the refrigerant liquefied in the condenser 24 to the heater 22 by the pump 25 , the refrigerant circulates through the above-mentioned elements of the Rankine cycle 2 .

Here, in the present embodiment, the expander 23 and the pump 25 are integrally connected, and a "pump-integrated expander 28" having a common rotating shaft 28a is configured. That is, the rotating shaft 28 a of the pump-integrated expander 28 has a function as an output shaft of the expander 23 and a function as a drive shaft of the pump 25 .

The transmission mechanism 3 has: a pulley 32 mounted on the rotating shaft 28a of the pump-integrated expander 28 via an electromagnetic clutch 31; a crank pulley 33 mounted on the crankshaft 50a of the engine 50; The belt 34 is wound around the pulley 32 and the crankshaft pulley 33 . The on (connection)/off (release) of the electromagnetic clutch 31 is controlled by the control unit 4, whereby the transmission mechanism 3 can communicate between the engine 50 and the Rankine cycle 2 (more specifically, the pump-integrated expander 28). ) to transmit/cut power between.

The detection signals of various sensors such as the first pressure sensor 61, the second pressure sensor 62, and the temperature sensor 63 are input into the control unit 4, wherein the first pressure sensor 61 detects the high-pressure side pressure PH of the Rankine cycle 2 , the second pressure sensor 62 detects the low-pressure side pressure PL of the Rankine cycle 2, and the temperature sensor 63 detects the temperature Ta of the outside air. In addition, when starting the Rankine cycle 2, the control unit 4 executes the activation control of the Rankine cycle 2 described later (hereinafter simply referred to as “Rankine activation control”).

Here, the high-pressure side pressure PH of the Rankine cycle 2 refers to the pressure in the refrigerant circulation passage 21 in the section from the pump 25 (the outlet) to the expander 23 (the inlet) via the heater 22 , and the Rankine cycle 2 The low-pressure side pressure PL of is the pressure in the refrigerant circulation passage 21 in the section from (the outlet of) the expander 23 to the (inlet) of the pump 25 via the condenser 24 . In addition, in this embodiment, the first pressure sensor 61 detects the pressure on the inlet side of the expander 23 (the outlet side of the heater 22 ) as the high-pressure side pressure PH of the Rankine cycle 2, and the second pressure sensor 52 detects the pressure on the pump side. 25 inlet side (condenser 24 outlet side) is detected as the low-pressure side pressure PL of the Rankine cycle 2 .

Next, the Rankine start control executed by the control unit 4 will be described.

The pump 25 is a liquid-feeding pump on the premise that the refrigerant on the inlet side of the pump 25 is in a liquid state (liquid refrigerant). However, if, for example, the pump 25 is installed at a position higher than the liquid level of the refrigerant in an unillustrated liquid tank (Japanese: レシーバタンク) due to layout constraints, etc., when the Rankine cycle 2 stops, The refrigerant on the inlet side of the pump 25 may be in a gas phase state (gas refrigerant). In such a state where the gas refrigerant is mixed into the inlet side of the pump 25, even if the pump is operated, a sufficient amount of refrigerant circulation cannot be obtained, and it takes a long time to start the Rankine cycle 2, or there is a Rankine cycle. 2 Possibility of starting failure. Therefore, when starting the Rankine cycle 2, it is necessary to make the refrigerant on the pump inlet side as liquid refrigerant as possible in advance.

Here, it can be confirmed that by opening the bypass valve 27 and operating the pump 25 in a state where the gas refrigerant is mixed into the refrigerant on the inlet side of the pump 25, that is, by circulating the refrigerant bypassing the expander 23, The time for the refrigerant on the inlet side of the pump 25 to become substantially 100% liquid refrigerant can be shortened. This is considered to be because of the following reasons. That is, when the refrigerant is circulated through the expander 23, the refrigerant expands in the expander 23 to lower the low-pressure side pressure PL, thereby lowering the condensation temperature. Therefore, in the condenser 24, the temperature difference between the condensing temperature and the flowing air is reduced, and it is in an operating state in which the degree of supercooling (supercooling) of the refrigerant is less likely to increase.

In addition, the inventors have also confirmed that after the refrigerant is circulated by opening the bypass valve 27, when the refrigerant on the inlet side of the pump 25 is in a fully liquefied state, more specifically, when the refrigerant on the inlet side of the pump 25 becomes After approximately 100% liquid refrigerant, the bypass valve 27 is closed, so that the reliability of the start of the Rankine cycle 2 is improved.

Therefore, when starting the Rankine cycle 2, firstly, the pump 25 is operated with the bypass valve 27 open, and then, as long as the refrigerant on the inlet side of the pump 25 is in a sufficiently liquefied state, in other words, when it indicates condensation When the parameter of the condensing capacity in the device 24 reaches a predetermined value or more, closing the bypass valve 27 can improve the starting performance (starting speed and reliability) of the Rankine cycle 2, and can make the output of the Rankine cycle 2 negative. The run time of is the minimum required for the Rankine Cycle 2 to run efficiently.

Therefore, in the present embodiment, the control unit 4 firstly opens the bypass valve 27 to operate the pump 25, and then closes the bypass valve 27 when the parameter indicating the condensing capacity in the condenser 24 reaches a predetermined value or more. That is, the Rankine start control is executed in which the parameter indicating the condensing capacity of the condenser 24 is equal to or greater than a predetermined value as a valve closing condition of the bypass valve 27 .

Here, in the present embodiment, the pressure difference ΔP between the high-pressure side pressure PH and the low-pressure side pressure PL of the Rankine cycle 2 is used as a parameter indicating the condensation capability in the condenser 24 . The reasons are as follows.

When the proportion of liquid refrigerant at the inlet side of the pump 25 increases, the refrigerant flow rate increases, and the condensation capacity in the condenser 24 also increases (condensing capacity=refrigerant enthalpy difference before and after the condenser×refrigerant flow rate). Therefore, the refrigerant flow rate is a value indicating the strength of the condensing ability. In addition, there is a relationship between the refrigerant flow rate and the pressure loss of the refrigerant circuit (when the refrigerant flow rate increases, the pressure loss of the refrigerant circuit also increases), so when the bypass valve 27 is opened, the high pressure side and the low pressure side The pressure difference ΔP=the pressure loss of the refrigerant circuit, which is a value related to the refrigerant flow rate. Therefore, by detecting the pressure difference ΔP, it is possible to easily judge (detect) the condensing capacity of the condenser 24, and more specifically, it is possible to easily determine whether the refrigerant on the inlet side of the pump 25 is substantially 100% liquid refrigerant. Judgment (detection), and less and stable control such as fluctuation (Japanese: Hanching) of the above-mentioned pressure difference ΔP can be realized. In addition, by detecting the pressure difference ΔP, it is also possible to determine whether the expander 23 is in a state capable of generating power (driving force) after the bypass valve 27 is closed, that is, whether the startup of the Rankine cycle 2 is completed.

2 and 3 are flowcharts of Rankine start control.

The flow chart is started by entering, for example, a Rankine Cycle 2 work request or work permit.

In step S1, it is judged whether it judged as "failure to start" (refer to step S15 mentioned later). If it is not judged as "failure to start", that is, if it is the first Rankine start control, then enter step S2. Then enter step S3.

In step S2, an initial value of a valve closing judgment value (pressure) ΔPs1 for judging whether to close the bypass valve 27 is set. Basically, the valve closing judgment value set in advance as the pressure difference between the high-pressure side and the low-pressure side of the Rankine cycle 2 when a sufficient amount (approximately 100%) of liquid refrigerant is supplied to the inlet side of the pump 25 A reference value of ΔPs1 (for example, an arbitrary value between 0.1 MPa and 0.25 MPa) is set as the above-mentioned initial value.

However, when it is judged that the start has been completed after the valve closing judgment value ΔPs1 was updated in the previous Rankine start control, the stored updated valve closing judgment value ΔPs1 is set as the above-mentioned initial value (see Step S17 described later).

In step S3, the valve closing judgment value ΔPs1 is updated (incrementally corrected). Specifically, the valve closing judgment value ΔPs1 (ΔPs1←ΔPs1+ΔPhos) is updated by adding the currently determined (set) valve closing judgment value ΔPs1 to the correction value ΔPhos. The aforementioned correction value ΔPhos can be set to, for example, 0.02 MPa.

Here, an upper limit value is set to the valve closing determination value ΔPs1 , and the valve closing determination value ΔPs1 updated (incrementally corrected) in step S3 is limited to be equal to or less than the above upper limit value. In addition, the upper limit value used here can be set to any value between 0.25 MPa and 0.4 MPa, for example.

In step S4, a valve closing judgment value ΔPs1 used in step S10 described later is determined.

When the Rankine start control has just started and it is not judged as "start failure", the initial value set in step S2 (that is, the reference value of the valve closing judgment value ΔPs1 or the previous Rankine start The updated valve closing judgment value ΔPs1) updated and stored during the control is directly set as the valve closing judgment value ΔPs1 used in step S9.

On the other hand, when it is judged as "failure to start" in step S15 described later and the Rankine start control is re-executed, the valve closing judgment value ΔPs1 is set as the valve closing judgment value ΔPs1 used in step S10. . Therefore, each time "failure to start" is judged in step S15, the valve closing judgment value ΔPs1 used in step S10 is increased by increasing the correction value ΔPhos every time, but the valve closing judgment value ΔPs1 after correction (updated) It is limited to the above upper limit value or less.

In step S5, it is judged whether the bypass valve 27 is open. When the bypass valve 27 is closed, proceed to step S6, and when the bypass valve 27 is open, proceed to step S7.

In step S6, the bypass valve 27 is opened.

In this embodiment, when the Rankine cycle 2 is stopped, the bypass valve 27 is normally opened. Therefore, in the first Rankine start control, the above-described processing of step S6 is generally omitted. On the other hand, since the bypass valve 27 is closed (refer to step S12) when the Rankine start control is re-executed after the startup failure (refer to step S15 described later), the bypass valve 27 is closed in the above step S6. 27 open.

In step S7, it is determined whether or not the electromagnetic clutch 31 is turned on (connected). When the electromagnetic clutch 31 is not connected, that is, during the first Rankine start control, enter step S8, and when the electromagnetic clutch 31 is connected, that is, when the Rankine start control is carried out again, Go to step S9.

In step S8, the electromagnetic clutch 31 is turned on (connected). When the electromagnetic clutch 31 is turned on, the motor 50 drives the rotary shaft 28a to rotate to make the pump 25 work.

Through the steps S5 to S8 described above, the refrigerant is circulated bypassing the expander 23 .

In step S9 , it is determined whether or not a first predetermined time has elapsed since the start of the cycle of the refrigerant bypassing the expander 23 . That is, in the first Rankine start control, it is judged in step S8 whether the first predetermined time has elapsed after the electromagnetic clutch 31 is turned on, and when the Rankine start control is performed again, it is judged in step S6. It is judged whether or not the first predetermined time has elapsed since the bypass valve 27 was opened. When the first predetermined time has not passed, the process proceeds to step S10. On the other hand, when the 1st predetermined time has elapsed, it progresses to step S11, and progresses to step S12 after judging as "pressure failure". In addition, the above-mentioned first predetermined time is set in advance as the time when the pump 25 is operated by opening the bypass valve 27, and the refrigerant on the inlet side of the pump 25 is sufficiently liquefied (can be formed into approximately 100% liquid refrigerant), For example, it can be set to 120 seconds.

In step S10, it is judged whether the pressure difference ΔP between the high-pressure side pressure PH and the low-pressure side pressure PL of the Rankine cycle 2 is equal to or greater than the predetermined valve closing value ΔPs1 determined (set) in step S4. If the pressure difference ΔP is lower than the valve closing judgment value ΔPs1, the process returns to step S9, and if the pressure difference ΔP is equal to or greater than the predetermined value ΔPs1, the process proceeds to step S12.

In step S12, the bypass valve 27 is closed. Thereby, the refrigerant circulates through the expander 23 . In addition, after closing the bypass valve 27, it progresses to step S13.

Using the above steps S9 to S12, it is judged whether the above pressure difference ΔP reaches the valve closing judgment value ΔPs1 within the first specified time after the refrigerant starts to bypass the expander 23 to circulate, that is, whether the bypass valve 27 satisfies the The closing condition of the valve is judged. Also, when the pressure difference ΔP reaches the valve closing determination value ΔPs1 within the first predetermined time, the bypass valve 27 is closed to circulate the refrigerant through the expander 23 . On the other hand, when the pressure difference ΔP does not reach the valve closing judgment value ΔPs1 within the first predetermined time, it is judged as "pressure failure". In addition, here, when it is judged as "poor pressure", the bypass valve 27 is closed to circulate the refrigerant through the expander 23, but the electromagnetic clutch 31 may be disconnected (released) to make the Rankine Launch control ends.

Here, based on the temperature Ta of the outside air, the initial value of the valve closing judgment value ΔPs1 set in the above-mentioned step S2 (that is, the reference value of the valve closing judgment value ΔPs1 or the update value in the previous Rankine control) may be adjusted. The subsequent valve closing judgment value ΔPs1) is corrected. In this case, the lower the temperature Ta of the outside air, the higher the initial value of the valve closing determination value ΔPs1 is corrected.

When the temperature Ta of the outside air becomes lower, the heat dissipation performance of the condenser 24 increases, and the condensation temperature and the temperature of the refrigerant at the inlet of the pump 25 decrease. As a result, the temperature of the refrigerant at the inlet of the heater 22 on the high-pressure side also decreases, and the amount of refrigerant in the liquid phase increases inside the heater 22 . Therefore, the amount of refrigerant on the low-pressure side decreases, and the degree of subcooling at the inlet of the pump 25 also decreases. Therefore, under the condition of low outside air, the subcooling degree at the inlet of the pump 25 is hardly increased. That is, the inlet of the pump 25 is under the condition that the refrigerant is not easily liquefied. Therefore, when the temperature Ta of the outside air is low, if the same judgment reference value is used to judge whether to close the bypass valve 27, the refrigerant at the inlet of the pump 25 may not be sufficiently liquefied, and the Rankine Unfavorable state for start of cycle 2.

Therefore, the control unit 4 controls to correct the initial value of the valve closing determination value ΔPs1 to a higher value as the temperature Ta of the outside air becomes lower. In this case, the lower the temperature Ta of the outside air is, the later the time to close the bypass valve 27 will be, and the inlet of the pump 25 will be in a condition where the refrigerant can be fully liquefied. Therefore, the reliability of starting can be improved. For example, if the initial value of the valve closing judgment value ΔPs1 is about 0.15 MPa when the temperature Ta of the outside air is 25°C, then when the temperature Ta of the outside air is 5°C, the initial value of the valve closing judgment value ΔPs1 can be set to Set to about 0.2MPa.

Also, when the temperature Ta of the outside air is low, similarly, even if the flow rate of the outside air passing through (the outside of) the condenser 24 is increased, the heat dissipation performance of the condenser 24 can be improved. Therefore, the control unit 4 may input the vehicle speed, for example, from an engine control unit not shown, and correct the initial value of the valve closing determination value ΔPs1 based on the input vehicle speed. In this case, the higher the vehicle speed, the higher the initial value of the valve closing determination value ΔPs1 is corrected. Of course, the control unit 4 may correct (set) the initial value of the valve closing determination value ΔPs1 based on both the temperature Ta of the outside air and the vehicle speed.

Returning to FIG. 2 , in step S13 , it is determined whether or not a second predetermined time (<first predetermined time) has elapsed since the bypass valve 27 was closed in step S12 . When the second predetermined time has not passed, the process proceeds to step S14. On the other hand, when the 2nd predetermined time has elapsed, it progresses to step S15, and when it judges that "starting failed", it progresses to step S18. The second predetermined time used here is preset so that the pressure difference ΔP can reach the startup completion judgment value ΔPs2 for judging the completion of the startup of the Rankine cycle 2 during the normal operation (operation) of the Rankine cycle 2 (refer to The time of step S14) described below can be set to 30 seconds, for example.

In step S14, it is judged whether the pressure difference ΔP between the high-pressure side pressure PH and the low-pressure side pressure PL of the Rankine cycle 2 is equal to or greater than the start completion judgment value ΔPs2 (>valve closing judgment value ΔPs1). The start completion judgment value ΔPs2 is set according to the Rankine cycle 2, and can be set to, for example, 0.8 MPa. In addition, when the said pressure difference ΔP is lower than the start completion judgment value ΔPs2, it returns to step S13.

On the other hand, in step S14, if the above-mentioned pressure difference ΔP is equal to or greater than the start completion judgment value ΔPs2, the process proceeds to step S16, where it is judged that "start is complete", and the currently set (determined) valve closing value is set (determined) in step S17. The judgment value ΔPs1 is stored and this flow (ie, Rankine start control) is ended. In addition, the valve closing judgment value ΔPs1 stored in step S17 is set as an initial value of the valve closing judgment value ΔPs1 in the next Rankine start control (refer to the above step S2). However, when the initial value of the valve closing judgment value ΔPs1 set in the above-mentioned step S2 is corrected based on the temperature Ta of the outside air and the vehicle speed, the valve closing judgment value ΔPs1 stored in the step S17 is used as the subtraction value. The value after taking the correction amount due to the temperature Ta of the outside air and/or the correction amount due to the vehicle speed is taken into account.

In the above steps S13 to S17, after the bypass valve 27 is closed, whether the pressure difference ΔP reaches the start completion judgment value ΔPs2 within the second predetermined time is judged, when the pressure difference ΔP is within the second predetermined time When the startup completion judgment value ΔPs2 is reached, it is judged that the startup of the Rankine cycle 2 is completed. On the other hand, when the above-mentioned pressure difference ΔP does not reach the start completion judgment value ΔPs2 within the second predetermined time, it is judged as "failed to start" and moves to the process of "failed to start" (refer to FIG. 3, step S18 to step S23). ).

When the startup of the Rankine cycle 2 is completed, the expander 23 generates a driving force to drive the pump 25. When the driving force of the expander 23 exceeds the driving load of the pump 25, the excess driving force is supplied to the pump 25 via the transmission mechanism 3. engine 50 to assist engine output.

In step S18 ( FIG. 3 ), it is judged whether or not it is judged as "failure to start" a predetermined number of times (for example, 3 times to 5 times) in succession. When it is judged as "failure to start" for the specified number of times in succession, enter step S19 and judge as "unable to start", then open the bypass valve 27 in step S20, and disconnect the electromagnetic clutch 31 in step S21 (release ), and end this flow (Rankine start control). In this case, the Rankine cycle 2 does not work (runs). In addition, when it is judged as "unable to start", it is presumed that there is some abnormality in the Rankine cycle 2, such as insufficient refrigerant amount, so it is desirable to use a warning light or a display, etc., to turn off the Rankine cycle. 2 Report the presence of an abnormality to the occupants of the vehicle, etc.

On the other hand, when the determination of "failure to start" is less than the predetermined number of times, the process proceeds to step S22, and it is determined whether or not it is determined to be "defective pressure" (see step S11).

If it is not judged as "poor pressure", return to step S1, and re-execute Rankine start control (repeat). However, when the Rankine start control is performed again in this case, the valve closing judgment value ΔPs1 is updated (incrementally corrected) in step S3.

If it is judged as "poor pressure", after the judgment of "poor pressure" is reset (cleared) in step S23, return to step S5 and re-execute the Rankine start control (repeat). However, when the Rankine start control is restarted in this case, the valve closing judgment value ΔPs1 is not updated (incremental correction) unlike the Rankine start control that is restarted when the "pressure failure" is not judged.

Fig. 4 is a timing chart of the above Rankine start control.

When the Rankine cycle 2 is started, the electromagnetic clutch 31 is turned on with the bypass valve 27 opened (time t0). As described above, in the present embodiment, since the bypass valve 27 is opened when the Rankine cycle 2 is stopped, normally only the electromagnetic clutch 31 is turned on. However, when the bypass valve 27 is closed when the Rankine cycle 2 is stopped, the bypass valve 27 is opened and the electromagnetic clutch 31 is turned on. As a result, the pump 25 operates, and the refrigerant circulates while bypassing the expander 23 . In this way, the subcooling degree of the refrigerant at the outlet side of the condenser 24 increases, and the flow rate of the liquid refrigerant supplied to the high-pressure side of the Rankine cycle 2 increases, and the pressure difference ΔP between the high-pressure side pressure PH and the low-pressure side pressure PL also increases. rise.

In addition, when the above-mentioned pressure difference ΔP rises to the valve closing judgment value ΔPs1, the condensation performance in the condenser 24 is in a sufficiently high state, and it is judged that substantially 100% liquefied refrigerant (liquid refrigerant) is continuously supplied to the pump 25 inlet side, and close the bypass valve 27 (time t1). Thereby, the refrigerant circulates through the expander 23 .

When the bypass valve 27 is closed, the above-mentioned pressure difference ΔP rises at a faster rate, and when the above-mentioned pressure difference ΔP rises to the starting completion judgment value ΔPs2, it is judged that the expander 23 is in a state capable of generating driving force, that is, it is judged as The start of the Rankine cycle 2 is completed, and the Rankine start control ends (time t2).

Here, as shown by the dotted line in FIG. 4 , when the pressure difference ΔP does not reach the start completion judgment value ΔPs2 after the second predetermined time has elapsed after the bypass valve 27 is closed (time ta), it is judged as "startup". failure”, the bypass valve 27 is opened to allow the refrigerant to bypass the expander 23 again to carry out the refrigerant. That is, the Rankine start control is performed again. When the Rankine start control is re-executed after such a judgment of "failure to start", if it is not judged as "poor pressure", as shown in Figure 5, every time it is judged as "failure to start", that is, at Every time the Rankine start control is repeated, the valve closing judgment value ΔPs1 is increased by the correction value ΔPhos every time.

In addition, as shown by the dotted line in FIG. 4, when the first predetermined time elapses after the bypass valve 27 is opened and the electromagnetic clutch 31 is turned on, the above-mentioned pressure difference does not reach the valve closing judgment value ΔPs1 (time tb), judged as "bad pressure". In this case, the Rankine start control is then re-executed because it is judged as "failure to start". However, when the Rankine start control is restarted when it is judged as "poor pressure", the valve closing judgment value ΔPs1 is not increased, unlike when the Rankine start control is restarted when it is not judged as "poor pressure". fix.

Next, when it is judged as "failure to start" a predetermined number of times in succession, it is judged as "start not possible", the electromagnetic clutch 31 is disengaged, and the Rankine start control is terminated.

According to the above-mentioned embodiment, when the Rankine cycle 2 is started, the pump 25 is first operated with the bypass valve 27 opened, so even if gas refrigerant is mixed into the refrigerant on the inlet side of the pump 25 Under this condition, the above-mentioned gas refrigerant can also be eliminated quickly. Next, when the pressure difference ΔP between the high-pressure side pressure PH and the low-pressure side pressure PL of the Rankine cycle 2 reaches the valve closing judgment value ΔPs1, the bypass valve 27 is closed, so that the refrigerant on the inlet side of the pump 25 becomes approximately 100% liquid refrigeration. After refrigerant, the refrigerant can be quickly circulated through the expander 23 .

As a result, the starting performance (speed and reliability of starting) of the Rankine cycle 2 can be improved, and the running time during which the output of the Rankine cycle 2 is negative can be reduced as much as possible, that is, the use of the engine 50 to pump the engine 50 can be reduced as much as possible. 25 (and expander 23) to drive, so that the Rankine cycle 2 operates efficiently.

Here, when the pressure difference ΔP does not reach the start completion judgment value ΔPs2 after the second predetermined time has elapsed after the bypass valve 27 is closed, the Rankine start control is re-executed (repeatedly executed) to realize the operation of the pump 25 again. The liquefaction of the refrigerant on the inlet side (liquid refrigerant formation) can increase the probability that the Rankine cycle 2 will be activated.

In particular, when "failure to start" occurs without judging "poor pressure", by increasing and correcting the valve closing judgment value ΔPs1 every time the Rankine start control is executed, it is compared with the latest Rankine start control. In contrast, the refrigerant on the inlet side of the pump 25 is further liquefied (liquid refrigerant), and then the bypass valve 27 is closed. Thereby, it is possible to further increase the probability that the Rankine cycle 2 has been started.

In addition, when the above-mentioned pressure difference ΔP reaches the startup completion judgment value ΔPs2 within the second predetermined time after the valve closing judgment value ΔPs1 is increased and corrected, the valve closing judgment value ΔPs1 after the increase and correction is stored, and set It is set as the initial value of the valve closing judgment value ΔPs1 in the Rankine start control at the next start of the Rankine cycle 2 . Thereby, when the Rankine cycle 2 is started, the possibility that the Rankine cycle 2 has been started can be increased by the first Rankine start control.

As mentioned above, although preferred embodiment of this invention was demonstrated, this invention is not limited to the said embodiment, It goes without saying that deformation|transformation and change are possible based on the technical idea of this invention. Hereinafter, several modified examples will be listed.

(Modification 1)

In the above-described embodiment, the pressure difference ΔP between the high-pressure side pressure PH and the low-pressure side pressure PL of the Rankine cycle 2 is used as a parameter indicating the condensation capability in the condenser 24 . However, the present invention is not limited thereto, and the degree of subcooling (supercooling) of the refrigerant on the outlet side of the condenser 24 (inlet side of the pump 25) may be used instead of the above-mentioned pressure difference ΔP, or in the above-mentioned pressure difference In addition to ΔP, the degree of subcooling (subcooling) of the refrigerant on the outlet side of the condenser 24 (the inlet side of the pump 25 ) is added. In this case, the valve closing condition of the bypass valve 27 is that the degree of subcooling (supercooling) of the refrigerant on the outlet side of the condenser 24 (the inlet side of the pump 25 ) is equal to or greater than a predetermined value. In addition, in this case, a temperature sensor and a pressure sensor are provided between the condenser 24 (the outlet) and the pump 25 (the inlet), and the control unit 4 is based on the temperature detected by the temperature sensor and the temperature detected by the pressure sensor 52 . Calculate (detect) the degree of subcooling of the refrigerant based on the pressure obtained.

In addition, the control unit 4 controls to open the bypass valve 27 to operate the pump 25 when starting the Rankine cycle, and to close the bypass valve 27 when the degree of subcooling of the refrigerant on the outlet side of the condenser 24 reaches a predetermined value or more. Through valve 27. The aforementioned predetermined value (initial value) can be set to, for example, a value (refrigerant temperature) at which the refrigerant can sufficiently become a liquid refrigerant on the outlet side of the condenser 24. In addition, each time it is judged that "failure to start" , adding corrections to the above values. Also in this way, the same effects as those of the above-described embodiment can be obtained.

(Modification 2)

In addition, the flow rate of the liquid refrigerant sent from the pump 25 may also be used as a parameter indicating the condensation capability in the condenser 24 . This is because the higher the condensing capacity in the condenser 24 is, the higher the flow rate of the liquid refrigerant sent from the pump 25 will be. In this case, the valve closing condition of the bypass valve 27 is that the flow rate of the liquid refrigerant sent from the pump 25 is equal to or greater than a predetermined value. In addition, in this case, a flow sensor for detecting the flow rate of the liquid refrigerant is provided on the outlet side of the pump 25 .

In addition, the control unit 4 controls to open the bypass valve 27 to operate the pump 25 when starting the Rankine cycle, and to close the bypass valve 27 when the flow rate of the liquid refrigerant sent from the pump 25 reaches a predetermined value or more. . The predetermined value (initial value) in this case can be set as, for example, the flow rate sent from the pump 25 when the refrigerant on the inlet side of the pump 25 becomes sufficiently liquid refrigerant, and in addition, every time it is judged that "failure to start" , the above specified value shall be corrected by increment. Also in this way, the same effects as those of the above-described embodiment can be obtained.

In addition, the refrigerant flow rate is related to the pressure loss of the condenser 24 , therefore, the pressure difference between the inlet side and the outlet side of the condenser 24 can also be used as a parameter indicating the condensation capacity of the condenser 24 . In this case, the valve closing condition of the bypass valve 27 is that the pressure difference between the inlet side and the outlet side of the condenser 24 is a predetermined value or more. In addition, in this case, pressure sensors are respectively provided on the inlet side and the outlet side of the condenser 24 , and the control unit 4 calculates (detects) the pressure difference between the inlet side and the outlet side of the condenser 24 .

(Modification 3)

In addition, in the above-mentioned embodiment, the expander 23 and the pump 25 are configured as a "pump-integrated expander 28" connected by the same rotating shaft 28a, but as shown in FIG. 6, the expander 23 and the pump 25 may be separated. of. In this case, the waste heat recovery device 10 has a Rankine cycle 20 composed of an expander 23 and a pump 25 separately, a transmission mechanism 30 , and a control unit 4 .

The transmission mechanism 30 has: a crank pulley 33 attached to the crankshaft 50 a of the engine 50 ; and an expander pulley 36 attached to the output shaft of the expander 23 via the first electromagnetic clutch 35 . 23a; a pump pulley 38 mounted on the drive shaft 25a of the pump 25 via a second electromagnetic clutch 37; and a belt 39 wound around the crankshaft pulley 33, the expander pulley 36 and the pump On the belt pulley 38.

In addition, the control unit 4 is controlled so that when starting the Rankine cycle 20, the bypass valve 27 is first opened, and the second electromagnetic clutch 37 is connected to make the pump 25 work, and then when the condensing capacity in the condenser 24 is indicated, When the parameter reaches a predetermined value or more, the first electromagnetic clutch 35 is connected, and then the bypass valve 27 is closed. In this case as well, the same effects as those of the above-described embodiment can be obtained. Alternatively, the pump 25 may be set as an electric pump, and the control unit 4 may be configured to output a drive signal to the pump 25 .

(Modification 4)

In addition, in the above embodiment, the valve closing judgment value ΔPs1 is increased by the correction value ΔPhos every time it is judged as "failure to start", that is, every time the Rankine start control is repeated (see FIG. 5 ). However, the present invention is not limited thereto. For example, as shown in FIG. 7 , the increase amount of the valve closing determination value ΔPs1 (correction value ΔPhos) may be increased every time the Rankine start control is repeated. In this way, by gradually increasing the correction value ΔPhos every time the Rankine start control is repeated, it is possible to reduce the number of "start failures".

(Modification 5)

In addition, in the above embodiment, when the pressure difference ΔP reaches the startup completion judgment value ΔPs2 within the second predetermined time after the valve closing judgment value ΔPs1 is corrected to increase, that is, when the Rankine start control is repeated, In the case of completing the start of the Rankine cycle 2, the valve closing judgment value at that time (the valve closing judgment value after the increase and correction) ΔPs1 is stored, and the above-mentioned valve closing judgment value after storage is set as Rankine cycle 2 The initial value of the valve closing judgment value ΔPs1 in the Rankine start control at the first start. However, the present invention is not limited thereto. For example, as shown in FIG. 8, when the Rankine start control is repeatedly performed, the valve closing judgment value (set value) ΔPs1 in the Rankine start control at the time of the next start of the Rankine cycle 2 (by a large amount or (increase to the vicinity of the upper limit value) to increase the correction, and then, when the Rankine start control is not repeated (that is, no start failure occurs), each time the Rankine cycle 2 is started, the increase The valve closing judgment value ΔPs1 after large correction decreases. In this case, the amount of decrease in increasing the corrected valve closing judgment value ΔPs1 may be constant or variable.

Furthermore, in the Rankine start control using the reduced valve closing judgment value ΔPs1, when the above-mentioned pressure difference ΔP after closing the bypass valve 27 does not reach the startup completion judgment value ΔPs2 within the second prescribed time (ie, not completed In the case of the start of the Rankine cycle 2), the Rankine start control is re-executed using the valve closing judgment value ΔPs1 in the Rankine start control at the previous start of the Rankine cycle 2. In addition, when the startup of the Rankine cycle 2 is completed, the above-mentioned valve closing judgment value ΔPs1 is maintained. In addition, when the Rankine start control is further repeated, the valve closing correction value ΔPs1 may be corrected to increase each time the Rankine start control is repeated.

(Other modifications)

According to the waste heat recovery device of the above embodiment, the drive force of the expander 23 is used to assist the engine output, but the present invention can also be applied to a waste heat recovery device of a power regeneration system that uses the drive force of the expander 23 to rotate a generator. In this case, for example, the expander, the pump, and the generator motor can be integrated by being connected by the same rotating shaft.

In addition, the waste heat recovery device of the above-mentioned embodiment is mounted on a vehicle and recovers waste heat from the engine of the vehicle, but the present invention can also be applied to a waste heat recovery device that recovers waste heat from an external heat source (for example, waste heat from a factory waste heat recovery device for recycling and waste heat recovery device for recycling the waste heat of the engine of the construction machine).

(Symbol Description)

1, 10...Waste heat recovery device

2. 20...Rankine cycle

3, 30...transfer mechanism

31...Electromagnetic clutch

4…control unit

10…Engine

21...refrigerant circulation path

22...heater

23…Expander

24...condenser

25…pump

26...bypass channel

27...Bypass valve

28…Pump-integrated expander

61, 62... Pressure sensors.

Claims (10)

1. A waste heat recovery device, comprising: Rankine cycle, the Rankine cycle is equipped with a heater, an expander, a condenser and a pump in the circulation path of the refrigerant, wherein the heater uses waste heat from an external heat source to heat the refrigerant to make the refrigerant gas The expander expands the refrigerant passing through the heater to generate power, the condenser condenses the refrigerant passing through the expander, and the pump transfers the refrigerant passing through the condenser to the The heater sends out; a bypass flow path that circulates refrigerant around the expander; a bypass valve, the bypass valve opens and closes the bypass flow path; a pressure difference detection unit, the pressure difference detection unit detects the pressure difference between the high pressure side and the low pressure side of the Rankine cycle; and a control unit that executes start-up control of the Rankine cycle, operates the pump while opening the bypass valve, and then closes the bypass valve, When the pressure difference after closing the bypass valve does not reach the startup completion judgment value of the Rankine cycle within a predetermined time, the control unit repeatedly executes the startup control, and the control unit The valve closing condition of the bypass valve is changed every time the activation control is repeated. 2. The waste heat recovery device according to claim 1, characterized in that, As the activation control, the control unit operates the pump while opening the bypass valve, and then closes the pump when the pressure difference reaches a valve closing judgment value lower than the startup completion judgment value. control of the bypass valve. 3. The waste heat recovery device according to claim 2, characterized in that, The control unit increases the valve closing determination value every time the activation control is repeated. 4. The waste heat recovery device according to claim 3, characterized in that, The control unit increases an increase amount of the valve closing determination value every time the activation control is repeated. 5. The waste heat recovery device according to claim 3, characterized in that, The control unit stores a valve closing judgment value when the pressure difference after closing the bypass valve reaches the startup completion judgment value within the predetermined time, and sets the stored valve closing judgment value to Set as the initial value of the valve-closing judgment value in the start control at the next start of the Rankine cycle. 6. The waste heat recovery device according to claim 2, characterized in that, In the case where the startup control is repeated, the control unit increases and corrects the valve closing judgment value in the startup control at the next startup of the Rankine cycle, and then, when the startup control is not repeated, In the case of activation control, the valve closing determination value after the increase correction is decreased every time the Rankine cycle is activated. 7. The waste heat recovery device according to claim 6, characterized in that, When the control unit executes the startup control so as to decrease the valve-closing judgment value after the increase correction, when the pressure difference after closing the bypass valve does not reach within the predetermined time, In the case of the startup completion judgment value, the startup control is re-executed using the valve closing judgment value in the startup control at the previous startup of the Rankine cycle. 8. The waste heat recovery device according to claim 1, characterized in that, The expander and the pump in the Rankine cycle are integrally connected. 9. A waste heat recovery device, comprising: Rankine cycle, the Rankine cycle is equipped with a heater, an expander, a condenser and a pump in the circulation path of the refrigerant, wherein the heater uses waste heat from an external heat source to heat the refrigerant to make the refrigerant gas The expander expands the refrigerant passing through the heater to generate power, the condenser condenses the refrigerant passing through the expander, and the pump transfers the refrigerant passing through the condenser to the The heater sends out; a bypass flow path that circulates the refrigerant around the expander; a bypass valve, the bypass valve opens and closes the bypass flow path; a pressure difference detection unit, the pressure difference detection unit detects the pressure difference between the high pressure side and the low pressure side of the Rankine cycle; and a control unit configured to operate the pump with the bypass valve open when starting the Rankine cycle, and then close the bypass valve when the pressure difference reaches a predetermined value; valve, The control unit is controlled to close the bypass valve after the pressure difference reaches a first predetermined value, and when the pressure difference does not reach a startup completion judgment value higher than the first predetermined value within a predetermined time, In the case of , open the bypass valve, and then close the bypass valve when the pressure difference reaches a second predetermined value that is higher than the first predetermined value and lower than the startup completion judgment value. 10. The waste heat recovery device according to claim 9, characterized in that, The expander and the pump in the Rankine cycle are integrally connected.